Port-scavenged two-cycle internalcombustion engine



M. w. Amwmmm EMI/@W2 @GRT SGAVENGED TWO-CYCLE lNTENAL-COMBUSTEON ENGINE Fi@ E @Montags Patented Aug. 2, 1949 PRT-SCAVENGED TWO-CYCLE INTERNAL- COMBUSTION ENGENE .Karl V. Anderson, Milwaukee, Wis., assigner to Nordberg Manufacturing Co., Milwaukee, Wis., a corporation of Wisconsin Application January 24, 1947, Serial No. 724,119

` (Ci. 12s- 65) Claims.

This invention relates to two-cycle internal combustion engines with fuel injection into the cylinder and port scavenging. The fuel may be gaseous or liquid. The invention was developed ior a low compression engine using spark ignition, and will be described as so embodied, but is not limited thereto. Similar principles may be used with a compression-ignition cycle.

ln engines of the type above mentioned location of the scavenging and exhaust ports and of the hiel injector should be such as to secure good mixing of the fuel with air and to minimize mixing of exhaust gases with the air or fuel.

According to the invention, fuel is injected through the side of the cylinder, at a point which is overtraveled by the piston, but is above the head-end extremities of all ports. The scavenging ports are in arcuate series around the cylinder and so located as just to be cleared by the piston at its crank-end dead point. They are limited to a little more than 180 of arc measured around the cylinder and the fuel injector is on a geometrical element of the cylinder which approximately bisects that arc. The exhaust ports occupy the remainder of the circumference and are so located that toward the end of the outstrol-:e of the piston they start to open before the scavenging ports start to open and are fully exposed when the scavenging ports are about half exposed.

This timing of ports is conventional and not critical so far as the present invention is concerned, but the conguration of the scavenging ports is an important element of novelty. Scavenging ports in respective halves of the 180 arc are opposed in pairs and direct the air in paths which are secant to the cylinder, converge slightly and are confined to that half of the cylinder which is remote from the exhaust ports. Taking the piston head, at the crank-end dead point, as a reference plane the paths of entering scavenging air are at a comparatively small angle to this reference plane for the two ports nearest the exhaust side, the angle increasing for each successive pair ,of opposed scavenging ports counted away from the exhaust side.

As a result there are two wide thin streams of scavenging alr which meet in a sort of inclined dihedral. At the apex thereof the streams merge into a single stream up the side of the cylinder. This stream picks up the injected fuel, turns downward at the cylinder head and flows downward to the exhaust ports.

The fuel injector is so located as to discharge into the merging streams of scavenging air, and

so the fuel is entrained by this air and kept from entering the exhaust stream.

Tests with a full size transparent model, using smoke through the scavenging ports, indicate a tendency of the upowing stream to deflect hellcally. The direction of deiiection is neither constant nor cyclic. but is taken apparently at random. It may improve mixture with the fuel. It does not appear to cause mixture of scavenging air with exhaust.

The preferred embodiment of the invention as applied to a. low compression engine will now be described by reference to the accompanying drawings, in which:

Fig. l is a vertical axial section through a horizontal engine cylinder showing one of the two sets of scavenging ports and three of the exhaust ports.

Fig. 2 is a fragmentary sectional view on the line 2-2 of Fig. l.

Fig. 3 is a section on the line 3--3 of Fig. 2.

Fig. 4 is a sectional view through one of the scavenging air supply chambers taken approximately on the line II--Ii of Fig. 3.

The cylinder illustrated in Fig. 1 is one cylinder of a radial engine having a vertical crank shaft, the invention having been embodied successfully in such an engine. The position of the cylinder is not material to the invention.

The cylinder 6 is carried by an annular frame, a portion of which appears at l. The cylinder has a removable head 8 in which are mounted spark plugs 9 of usual form. No ignition circuit is illustrated but a conventional circuit would be used. v

The cylinder li and head have jacket spaces I I for the circulation of cooling water. The water connections are not fully illustrated but one .wat-er connection is shown at I2.

A trunk piston I3 with rings I4 works in the cylinder and defines therein a working space I5, between the at head of the piston and the oblate spheroidal inner wall of head 8. The piston I3 is connected by connecting rod IB with the crank of the engine. The crank shaft may be of any type and is` not illustrated. The piston is shown in Fig. 1 at its outer or crank-end dead point.

No novelty is claimed for any of the parts so far described, and they are subject to variation within a wide range.

The cylinder has a series of exhaust ports Il which extend around the cylinder through an arc of nearly They lead to a passage I8 cored around this portion, of the cylinder and having a discharge connection I9 leading to an exhaust manifold which is not illustrated. Measured from the head-end dead point the exhaust ports start to open at a crank angle of about 109 and are wide open at 145.

The scavenging air ports 2|, 22, 23l 24, 25, 26, 21, 28 are arranged in a series which extend around the cylinder 8 in an arc complementary to the arc of exhaust ports and hence a little more than 180. No ports are located between the points a: and y (see Fig. l2) and hence there are actually two series of opposed ports, as will be explained. The ports 2|-28 are fed by connection 29 and a passage 3| cored in the cylinder casting. The piston I3 starts to expose the scavenging ports at a crank angle of about 180 measured from the head-end dead point and they are wide open at the crand-end dead point.

The bounding surfaces of the scavenging port openings are nearly all warped surfaces in the geometrical sense. Referring to Fig. 3 the surfaces 32 and 33 of ports 2|, 22 (called end surfaces are substantially parallel with each other but are inclined. The inclination increases for successive pairs of ports; that is to say, there is an increasing component of direction toward the cylinder head for each successive pair of ports counted from the cylinder axis toward the cylinder wall. Thus air discharged through Iopposed ports 2| and 22 meets at a; that discharged by 23 and 24 meets at b and so on. The meeting areas a, b, c, d are on a line inclined as shown in Figs. 1 and 4.

That the ports are opposed in pairs is best shown in Fig. 2. This view illustrates the further fact that the lines of flow to the points a, b, c, d converge and are in that half of the cylinder remote from the exhaust ports Il. The webs which separate the ports 2|-28, inclusive, are streamlined, as best shown in Fig. 2.

The approximate effect is to deliver scavenging air in two thin streams which form a dihedral whose apex is a-d. Along a-d the two streams merge and then ow toward the cylinder head along the proximate side of the cylinder. The concave spheroidal form of this head favors return flow to the exhaust ports I1 without conflict with the outward stream.

Fuel 'is injected at the proper time (starting preferably about 170 of crank angle measured from the head-end dead point) by an injection device 34 here illustrated as the gas injection valve yof my copending application Serial No. 699,698,

led September 27, 1946. A Diesel type oil injecticn valve or other liquid or gas fuel injecting device could be substituted.

Fuel is` injected toward the line a-d and hence directly into the merging flows of scavenging air. This favors good mixture of fuel with the air, and assures that entering fuel will be entrained by the air and so will not pass across the cylinder into the exhaust stream.

As stated, there is reason to believe that flows in the cylinder have a moderate helical component which reverses more or less at random in successive cycles, but this eiect results from accidental factors not yet identified. The invention is disclosed on the basis of structure, and will be so claimed without reliance on the presence or absence of particular ow characteristics.

The number of exhaust or scavenging ports is not significant as to the invention, since the number is determined by the need of grids to carry the piston rings over the ports. The unattainable ideal is elimination of grids. 'This would.

aord two sheet-like streams of scavenging air which converge and enclose a volume into which the fuel is injected. The air streams, as they merge, entrain the fuel and carry it in a stream which follows the exhaust ow substantially to but not through the exhaust ports.

This action and the related location of the fuel injecting valve are the most significant features of the invention and modifications which avail of the principle are within the scope of the invention.

What is claimed is:

1. In a port-scavenged two-cycle internal combustion engine, thecombination of a cylinder having an arc of exhaust ports and arcs of scavenging ports, the two types of ports each subtending opposite approximately o portions of the cylinder circumference, the exhaust ports being so locatedas to be exposed by the piston before the scavenging ports are exposed, and the scavenging ports being formed as to direct two fiat streams of-scavenging air` with components of motion toward the head-end of the cylinder and away from the exhaust ports to a line of mergence in that half of the cylinder bore which is remote from the exhaust ports; a piston reciprocable in the cylinder and controlling said ports; and fuel injecting means mounted in the side of the cylinder opposite said exhaust ports and arranged to direct fuel into said merging air streams.

2. In a port-scavenged two-cycle internal combustion engine, the combination of a cylinder having an arc of exhaust ports and two arcs of scavenging ports, the two arcs o'f scavenging ports being separated by an unported arc and in the aggregate including said unported arc subtending not materially more than half of the cylinder circumference, the exhaust ports being opposite said unported arc and so located as to be exposed by the piston before the scavenging ports are exposed, and the scavenging ports being formed as to direct two fiat streams of scavenging air with components of motion toward the head-end of the cylinder and away from the exhaust ports to a line of mergence in that half of the cylinder bore which is remote from the exhaust ports; a piston reciprocable in the cylinder and controlling said ports; and fuel injecting means arranged to direct fuel into said merging air streams.

3. In a port-scavenged two-cycle internal combustion engine, the combination of a cylinder having an arc of exhaust ports and arcs of opposed scavenging ports, the two types of port each subtending approximately 180L1 of the cylinder circumference, the exhaust ports being so located as to open first, the scavenging ports being opposed to one another in pairs and arranged to direct air in converging secant lines lying within approximately one-half of the cylinder bore, successive secant lines counted from cylinder axis toward the cylinder wall having an increasing component of direction toward the cylinder head, whereby the scavenging air flows in two flat streams which meet and merge along a line inclined to the cylinder axis; a piston reciprocable in said cylinder and controlling said ports; and a fuel injection valve mounted in the side of said cylinder and arranged to direct fuel into said merging air streams.

4. In a port-scavenged two-cycle internal combustion engine, the combination of a cylinder having an arc of exhaust ports and two arcs of opposed scavenging 'ports separated by an unported arc, the two types of port each subtending at least major portions of respective opposite halves of the cylinder circumference, the exhaust ports being so located as to open first, the scavenging ports in the two arcs being symmetrical in pairs with reference to a diameter of the cylinder bore and arranged to direct air in secant lines lying within approximately that half of the cylinder bore which is remote from the exhaust ports, the scavenging ports having graduated components of direction toward the cylinder head whereby mergence of flows occurs along a line oblique to the cylinder axis; a piston reciprocable in said cylinder and controlling said ports; and a fuel injection valve arranged to direct fuel into said merging air streams.

5. In a port scavenged two-cycle internal combustion engine, the combination of a cylinder having an arc of exhaust ports at one side of the cylinder, and two arcs of scavenging ports in which the ports are arranged in pairs opposed to each other and formed to direct air streams in converging planes within that half of the cylinder remote from the exhaust ports, successive streams counted in a direction away from the exhaust ports having increasing components of direction toward the cylinder head whereby mergence of flows occurs along a line oblique to the cylinder axis, the exhaust ports being so located as to open first; a piston reciprocable in said cylinder and controlling said ports; and a fuel injection valve arranged to direct fuel toward said line of mergence.

KARL V. ANDERSON.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS 

